I. Field of the Invention
The present invention relates to slurry piston pumps, and more particularly, to such pumps for pumping concrete and the like.
II. Description of Prior Art
Piston pumps are often utilized to pump thick slurry mixes (examples of which include concrete, cement, stucco, mortar, gypsum, sludge, silt, mud and topsoil, and bentonite) for construction and remediation purposes. By way of example, a concrete pumping truck may include a swing tube which swings back and forth within a concrete hopper mounted at the back end of the truck. A piston pump, or a pair of piston pumps in a dual pump, communicate with the concrete hopper and swing tube.
Each piston pump includes a drive cylinder which has a drive rod extending therefrom, with a piston mounted to the exposed end of the drive rod. The piston extends into a piston cylinder, the back end of which is axially aligned with the drive cylinder, and the front end of which communicates into the hopper or with the swing tube, depending on the position of the swing tube. As a consequence, as the drive rod reciprocates within the drive cylinder, the piston is caused to move between the back and front ends of the piston housing. In the back stroke (during which the piston moves in a direction away from the front end and towards the back end), the front end of the piston cylinder opens into the hopper to pump concrete into the piston housing through the front end thereof. In the forward stroke (during which the piston moves in a direction away from the back end and towards the front end), the front end of the piston cylinder is advantageously coupled to the swing tube so as to pump the concrete from within the piston cylinder out through the swing tube, to a delivery hose coupled to the end of the swing tube so as to pump the concrete to the construction or remediation site.
Where a pair of such piston pumps are employed, the drive rods will typically reciprocate in opposite directions such that one pump is in the back stroke while the other is in the forward stroke. The swing tube shifts back and forth between the front ends of the two piston pump cylinders so as to couple to one of the piston pumps in the forward stroke for pumping of concrete from that piston cylinder, while the second piston pump communicates into the hopper to pump concrete into the piston cylinder of the second pump.
In conventional slurry piston pumps, whether a one piston pump or a dual piston pump, the nature of the slurry material involved creates a significant amount of debris and buildup which can interfere with the proper operation of the piston pump. As a consequence, it has been conventional practice to provide a so-called water box between the drive cylinder and the piston cylinder. The drive cylinder is typically attached to one side of the water box with the piston cylinder being attached to the opposite side of the water box. The result is to axially align the cylinder with a fluid receiving space therebetween defined by the water box. Thus, the drive rod extends from the drive cylinder, through the water box, and into the pump cylinder. As the drive rod traverses through the water box, it is cleaned or lubricated by the fluid in the water box. Additionally, the fluid in the water box is carried into and out of the piston cylinder behind the piston as it moves therein so as to clean or lubricate the interior wall of the piston cylinder as well.
Use of the water box, however, presents certain drawbacks. In the first instance, the length of the drive rod must be sufficient not only to properly move the piston through the piston cylinder between the ends thereof, but must also take into account the length of the fluid receiving space introduced between the drive cylinder and the piston cylinder by virtue of the water box interposed therebetween. Thus, the drive rod (and its associated cylinder) must be made sufficiently long to traverse the water box and to move the piston within its cylinder. Shorter drive rods (and associated cylinders) are, however, desired.
Additionally, the respective cylinders are coupled to the water box by bolts and nuts and the like, some parts of which are accessible only through the interior of the water box. A typical water box may be accessible through an opening in the top. Liquid may be added through that opening. Access to the interior of the water box in order to reach the components attaching the cylinder housings thereto for maintenance and repair is also by that top opening. However, the area over the top of the water box can be difficult to access. In many situations, the piston pumps form part of a larger pumping system, such as a concrete pumping truck. The piston pumps are usually situated in very tight quarters with respect to the rest of the pumping system making access to the water box, and especially the interior thereof, very difficult.
The water box my also have a lid over the top opening. Often, the lid does not stay in place. As a consequence, the liquid in the water box, as well as any debris from the slurry material, may slosh out of the water box creating a spill hazard, especially during use or movement of the pump system with its attendant jostling and the like.
The present invention provides a slurry piston pump which eliminates the water box and its attendant drawbacks. To this end, and in accordance with the principles of the present invention, a fluid hose is coupled into the back end of the piston cylinder through the cylinder wall and is situated radially outwardly therefrom so as to provide a reservoir for the cleaning or lubricating fluid. The fluid hose has a proximal or cylinder end coupled, such as through a fitting, to communicate directly into the back end of the pump cylinder through the cylinder sidewall, rather than from axially behind the cylinder as in the case of a water box. The fluid hose is thus coupled to expose the drive rod and the back side of the piston to the fluid as the drive rod reciprocates the piston through the piston cylinder, but without the need for a water box between the drive and piston cylinders and the disadvantages that would present. Instead, the drive cylinder may be coupled directly to the piston cylinder thereby shortening the length of the drive rod (and its associated cylinder). Additionally, the fluid hose may be flexible, and/or coupled to the piston cylinder by a fitting that is rotatably mounted to the piston cylinder sidewall, so that the fluid hose may be routed comfortably within tight quarters, but otherwise accessible as necessary. The hose may have a distal end fluidically remote from the cylinder end and through which fluid may be introduced into, or removed from, the hose. Access to the distal end is accomplished simply by manipulating the hose or rotating it about the coupling.
Where the piston pump has its own fluid hose, the distal end thereof may have a removable cap so as to selectively seal the fluid hose and the related piston cylinder. As a result, the fluid and any debris is kept from splashing out and creating a hazard while the piston pump is in use or being transported. If the hose is held in an upward vertical orientation, the cap may be vented so as to allow fluid to enter and leave the fluid hose from or to the piston cylinder without expelling out of the fluid hose or building up pressure therein. Alternatively, an expandable chamber or reservoir may be included in the hose or cap to accommodate pressure changes in the hose.
The above may be applied to individual slurry piston pumps whether a single, dual or other multiple pump piston system is employed. However, where a dual pump system is employed, it may be advantageous to couple together the fluid hoses associated with each piston cylinder. To this end, a fluid hose may extend between the back ends of the two piston cylinders so as to fluidically couple them through the same hose thereby exposing both drive rods and piston cylinders to the fluid in the hose. The hose in the dual piston pump system may be comprised of two separate hoses, referred to in that case as hose sections, each with a cylinder end coupled to the respective piston cylinders. A further fitting may be provided to selectively couple the distal ends of the hose sections together into, effectively, a single fluid hose. The flexibility of the hose and/or the rotatable fittings at the piston cylinders allows the hose to be situated in tight quarters, yet access thereto is easily gained. To fill the hose with liquid, or remove liquid therefrom, the further fitting joining the sections together may be unclamped or otherwise opened to thereby gain access to the distal end(s) of the hose section(s).
By virtue of the foregoing, there is thus provided a slurry piston pump which eliminates the water box and its attendant drawbacks.